1. Field of the Invention
This invention relates to a tape cartridge having a tape reel rotatably received within a body of the tape cartridge, with a magnetic tape wound around the tape reel.
2. Description of the Related Art
As a tape cartridge of this kind, the present applicant has already developed a magnetic tape cartridge 51 shown in FIGS. 5 to 7 (hereinafter simply referred to as xe2x80x9cthe tape cartridgexe2x80x9d).
As shown in FIG. 5, this tape cartridge 51 is comprised of a casing body (cartridge body) 2, a tape reel 52, a lock member 4, a spring 5, a brake release plate 53, and a pin member 7. It should be noted that the tape reel 52 has a magnetic tape wound therearound, but for ease of understanding of construction of each component, illustration of the magnetic tape is omitted. Further, a leading end of the magnetic tape is wound around the pin member 7 and fixed by a fixing tool 7a. The pin member 7 guides the magnetic tape to a take-up reel within a record/playback apparatus when it is moved along a tape traveling passage within the record/playback apparatus to the take-up reel.
As shown in FIG. 5, the casing body 2 is comprised of a pair of cartridge halves (an upper casing 11 and a lower casing 12), which are shallow plate-shaped and can be fitted to each other, and a shutter member 2b which can close a tape draw-out slot 2a formed by the upper casing 11 and the lower casing 12 when they are fitted. Further, as shown in FIG. 7, from an inner surface of the upper casing 11 perpendicularly extend four guide projections 11a, 11a, 11a, 11a for mounting the lock member 4 such that the lock member 4 cannot be rotated but is allowed to move vertically. Further, as shown in FIG. 5, the lower casing 12 has an insertion hole 12a formed therethrough for allowing a driving shaft S (see FIG. 7) of the record/playback apparatus to be inserted therein.
As shown in FIG. 5, the tape reel 52 is comprised of a hub 54, a pair of flanges (an upper flange 55 and a lower flange 56), and a metal plate 18. The hub 54 is formed to have a bottomed cylindrical shape around which a magnetic tape can be wound, and integrally formed with the lower flange 56. Further, as shown in FIG. 6A, teeth 56a for meshing with the lock member 4 are formed on an inner surface of the lower flange 56 surrounded by the hub 54, and three insertion holes 56b, 56b, 56b for mounting the brake release plate 53 in a vertically movable fashion extend to an outer surface of the lower flange 56 in a communicating fashion (see FIG. 6B). Further, as shown in FIG. 5, the upper flange 55 is formed therethrough with an insertion hole 55a allowing insertion of the lock member 4 and the brake release plate 53. Further, as shown in FIG. 6B, at a location of the outer surface of the lower flange opposed to the insertion hole 12a of the lower casing 12, driving teeth 56c, 56c, 56c are formed on an identical circumference. Further, an area inward of the driving teeth 56c, 56c, 56c, there is mounted the metal plate 18 (see FIG. 5) for causing the tape reel 52 to be magnetically attracted to the driving shaft S. The hub 54, the upper flange 55, and the lower flange 56,which form the tape reel 52 are each made by resin molding. The driving teeth 56c is demanded of a high strength since it is meshed with the driving teeth of the driving shaft S of the record/playback apparatus. Therefore, the driving teeth 56c, the hub 54, and the lower flange 56 are integrally formed from a mixed resin material in which a reinforcing material, such as a glass fiber, is mixed in a natural resin material (pure resin material not containing a pigment (opaque material which neither reacts with a material mixed therewith, nor dissolves in water or alcohol, but exhibits a certain color; an inorganic material, such as a metal salt), a dye, or a reinforcing material, the definition being applied hereinafter), such as polycarbonate. On the other hand, the upper flange 55 is not demanded of such a high strength as the lower flange 56, since the upper flange 55 is not brought into contact with the record/playback apparatus. Therefore, the upper flange 55 is formed by resin molding by using the natural resin material having no reinforcing material mixed therein. Further, the upper flange 55 is formed by using the natural resin material used in forming the lower flange 56, in view of facility of ultrasonic welding of the upper flange 55 to the lower flange 56.
The lock member 4 has a bottom formed with teeth 4a which can be meshed with the teeth 56a of the lower flange 56, and a protrusion 4b which can be brought into contact with a center of the brake release plate 53, as shown in FIGS. 5 and 7. Further, a positioning protrusion 4c in the shape of a cross in plan view extends perpendicularly from an upper surface of the lock member 4. In this case, the protrusion 4b has a function of decreasing the sliding resistance offered when the brake release plate 53 rotates together with the tape reel 52, by bringing the lock member 4 into point contact with the brake release plate 53. Further, the positioning protrusion 4c is formed with a guide groove 4d in the shape of a cross into which the four guide projections 11a, 11a, . . . of the upper casing 11 can be inserted. Further, by having the protrusions 11a, 11a, . . . inserted into the guide groove 4d, the lock member 4 is attached to the upper casing 11 in a rotation-inhibited but vertically movable fashion, and constantly urged toward the inner surface of the lower flange 56 (toward a brake position) by the spring 5.
The brake release plate 53 is formed as a thin flat plate from a resin material, as shown in FIG. 7, and three legs 53a, 53a, 53a which can be inserted into the insertion holes 56b, 56b, 56b of the lower flange 56 extend perpendicularly from a reverse surface thereof. The brake release plate 53 is attached to the inside of the hub 54 in a state in which the legs 53a, 53a, 53a thereof are inserted into the insertion holes 56b, 56b, 56b of the lower flange 56, respectively. Thus, the brake release plate 53 is configured such that it is vertically movable with respect to the lower flange 56 within a range of the length of the legs 53a, 53a, 53a, and at the same time, it cannot be rotated relative to the lower flange 56. Therefore, the brake release plate 53 is rotated together with the hub 54 and the lower flange 56 during rotation of the tape reel 52.
According to the tape cartridge 51, when it is taken out of the record/playback apparatus, the lock member 4 is constantly urged toward the inner surface of the lower flange 56 (toward the brake position) by the spring 5, within the casing body 2. Further, the teeth 4a of the lock member 4 and the teeth 56a of the tape reel 52 are brought into mutual contact and meshed with each other. In this state, since the teeth 4a of the lock member 4 are meshed with the teeth 56a of the tape reel 52, and at the same time, the guide protrusions 11a, 11a, . . . of the upper casing 11 are inserted into the guide groove 4d of the lock member 4, rotation of the tape reel 52 within the casing body 2 is inhibited by the lock member 4. Therefore, loosening or collapse of winding of the magnetic tape wound around the tape reel 52 within the casing body 2 is prevented. Further, in this sate, the brake release plate 53 is pressed against the inner surface of the lower flange 56 by the lock member 4 urged by the spring 5, so that the legs 53a, 53a, 53a of the brake release plate 53 extend through the insertion holes 56b,56b, 56b of the lower flange 56 to be projected out from the outer surface of the lower flange 56.
On the other hand, when the tape cartridge 51 is loaded in the record/playback apparatus, the record/playback apparatus causes the shutter member 2b to be slid to open the tape draw-out slot 2a. Then, as shown in FIG. 7, the driving shaft 7 is magnetically attracted to the metal plate 18 of the tape reel 52, so that the driving teeth of the driving shaft S are meshed with the driving teeth 56c of the tape reel 52. At this time, the legs 53a, 53a, 53a of the brake release plate 53 are lifted upward by the driving shaft S while holding the protrusions 4b of the lock member 4 are held in point contact with the brake release plate 53. This causes the lock member 4 to be pushed upward toward the inner surface of the upper casing 11 by the guide of the guide protrusions 11a, 11a, . . . . As a result, the meshing of the teeth 4a of the lock member 4 with the teeth 56a of the lower flange 56 is released, thereby allowing rotation of the tape reel 52. Subsequently, the tape reel 52 is rotated along with rotation with the driving shaft S. At this time, the magnetic tape wound around the tape reel 52 is drawn out of the tape draw-out slot 2a by the record/playback apparatus, whereby various recording data are recoded on or read from the magnetic tape.
This tape cartridge 51, however, has the following points which should be improved: In this tape cartridge 51, to increase the strength of the driving teeth 56c of the tape reel 52 for meshing with the driving teeth of the driving shaft S, the lower flange 56 and the hub 54 which are integrally formed with the driving teeth 56c are formed by using the mixed resin material in which the reinforcing material is mixed in the natural resin material. The driving teeth 56c, the lower flange 56, and the hub 54 formed by using the mixed resin material have minute irregularities on their surfaces due to inclusion of the reinforcing material in the mixture, which degrades smoothness of the surfaces. This may produce transferred wrinkles of the magnetic tape wound around the hub due to the irregularities formed on the surface of the hub 54, and if the transferred wrinkles are large, they can increase signal dropout. At present, the dropout caused by the transferred wrinkles do not raise problems in the market (among users). However, to provide for the high-density data recording in the future, it is preferable to improve the tape cartridge such that occurrence of transferred wrinkles is prevented for further reduction of the dropout for the tape cartridge.
It is a main object of the invention to provide a tape cartridge which is capable of reliably preventing dropout of a magnetic tape without lowering durability thereof.
(1) To attain the above object, a tape cartridge according to the present invention includes a cartridge body formed by a pair of cartridge halves, one of the cartridge halves being formed with an insertion hole permitting insertion of a driving shaft of a record/playback apparatus, and a tape reel formed by a hollow cylindrical hub and a pair of flanges, the tape reel being accommodated within the cartridge body, with a tape wound around the hub, wherein a center line average height Ra of a surface of the hub is defined to be not smaller than 0.005 xcexcm and not larger than 0.04 xcexcm. Here, the center line average height Ra is a surface roughness defined in JIB B 0601 (ISO 486:82, 3274:75, 4287-1:84, 4287-2:84; 4288:85).
According to this tape cartridge, by defining the center line average height Ra of the surface of the hub to be not smaller than 0.005 xcexcm and not larger than 0.04 xcexcm, it is possible to maintain an excellent smoothness of the surface of the hub. Therefore, occurrence of dropout of the magnetic tape can also be prevented due to the excellent smoothness of the hub, whereby reliability of the tape cartridge can be enhanced.
(2) In this case, it is preferred that the center line average height Ra of the surface of the hub is defined to be not smaller than 0.005 xcexcm and not larger than 0.02 xcexcm. This makes it possible to secure a sufficient margin for the requirement of smoothness, so that it is possible to realize the tape cartridge 1 having a high reliability which is hard to suffer dropout even under severer use conditions. Further, it is possible to realize a tape cartridge which can maintain a high reliability over a long term.
(3) Further, by forming the hub from a natural resin material, the center line average height Ra of the surface of the hub can be reliably and easily set to a value not smaller than 0.005 xcexcm and not larger than 0.02 xcexcm. This enables the smoothness of the surface of the hub to be reliably maintained in an excellent condition.
(4) To attain the above object, a tape cartridge according to the present invention includes a cartridge body formed by a pair of cartridge halves, one of the cartridge halves being formed with an insertion hole permitting insertion of a driving shaft of a record/playback apparatus, and a tape reel formed by a hollow cylindrical hub and a pair of flanges, the tape reel being accommodated within the cartridge body, with a tape wound around the hub, and the one flange located on a side of the insertion hole has a surface opposed to the insertion hole, the surface being formed with driving teeth for meshing with the driving shaft, and is formed from a mixed resin material in which a reinforcing material is mixed in a natural resin material, the hub being formed integrally with the other flange, from a natural resin material.
According to the tape cartridge, by forming the one flange located on a side of the insertion hole integrally with driving teeth for meshing with the driving shaft, from a mixed resin material, and at the same time forming the other flange integrally with the hub, from a natural resin material, it is possible to increase the strength of the driving teeth, and hence maintain a high durability of the cartridge. Moreover, since the center line average height Ra of the surface of the hub can be reliably made not larger than 0.02 xcexcm, it is possible to maintain the smoothness of the surface of the hub in an excellent condition. Therefore, it is possible to provide a tape cartridge having an excellent durability which does not incur wear or deformation of the driving teeth. Further, due to the excellent smoothness of the surface of the hub, occurrence of dropout of the magnetic tape can be prevented, thereby enhancing the reliability of the tape cartridge.
(5) Further, as the natural resin material, it is preferable to use PC (polycarbonate), PA (nylon (generic name of a long-chain polyamide having repetition of a polyamide group as an indispensable part of a main chain of a polymer)), PBT (polybutylene terephthalate), or PPS (polyphenylene sulfide). These natural resin materials are inexpensive materials, so that it possible to construct the hub at a low cost while maintaining the smoothness of the surface of the hub.
(6) Further, it is preferable to use, as the reinforcing material, a glass fiber, a carbon fiber, or a metal powder. These reinforcing materials are inexpensive materials, and hence the durability of the one flange and driving teeth can be enhanced without increasing the manufacturing costs of the tape cartridge.
It should be noted that the disclosure of the present specification relates to the subject included in Japanese Patent Application No. 2001-139641 which was filed on May 10, 2001, and all of the disclosure thereby is expressly incorporated herein by reference.